The present invention relates to agricultural tillage apparatus; and more particularly, it relates to apparatus which may be used for primary tillage at relatively high ground speeds (in the range of 41/2 to 8 mph). The invention uses a combination of discs and plow points which accomplishes complete tillage in one pass without double-working of the soil by the discs and performs some deep soil breaking with the points, but which is especially adapted to leave the surface of the soil relatively even and without deep furrows and to avoid creating a plow sole.
Perhaps the most commonly used tool for plowing is the conventional moldboard plow. Usually the plow bottom is set at a particular depth of plowing, for example eight or ten inches. Moldboard plows typically are mounted to a main beam which is inclined relative to the direction of travel of a tractor so that each moldboard is set to take a swath or strip of ground which typically may be 12-16 inches wide or more, cut it into a slab or large chunks (clods), and roll the ground over into a furrow formed by the next forward moldboard. The leading moldboard turns its strip of ground (usually in the form of a slab) over into a furrow formed on a previous pass of the plow system.
When a moldboard plow is used repeatedly to plow ground at the same depth, a layer of highly compacted soil is formed just beneath the worked soil. This is called the plow "sole", and it has the disadvantage that, due to its compactness, roots of plants have difficulty in penetrating it; and due to its relative flatness, water has a tendency to drain over the plow sole rather than being absorbed by the soil. A moldboard plow displaces to one side all of the soil that is tilled, leaving deep furrows on the surface.
Each adjacent swath is worked in the same direction. That is, a farmer cannot till a strip one direction, turn around and till the adjacent strip in the opposite direction. He must always have the untilled soil to the same side. Eventually, the soil must be plowd in the opposite direction, and even when this occurs, a deep side ridge normally is left at the end strip.
It is desirable to plow deep soil in large slabs or clods, particularly during the fall because over the winter, water will be absorbed in the fissures and interstices thus formed; and the freezing and thawing over the winter will make the soil more mellow in the spring, and thereby facilitate the preparation of seed beds. However, there are some areass such as rolling fields where it is not desirable to leave the deep surface furrows left by a moldboard plow which have a tendency to cause runoff of surface water which erodes top soil and prevents storing the water in the subsoil which is highly desirable. There is some question as to whether the benefits of such deep turning of all the subsoil are worth the extra energy necessary to accomplish it.
In the case where moldboard plows are used for tilling soil which has not previously been cleared, and may contain some "trash" (that is, crop residue which, in the case of corn, may be bulky and tough), a coulter is usually located in front of each moldboard plow to cut through the trash and at least partly through the soil. This reduces accumulation of trash on the leading edge of the moldboard, and it further assists the moldboard by cutting the soil. Coulters are also used in connection with other tillage systems, and they generally are in the form of a relatively flat, circular blade mounted to rotate about an axis transverse of the direction of travel.
Another form of blade that is used in tillage systems is referred to as a "disc", and it takes the shape of a spherical or frusto-conical dish or bowl. They are found primarily in disc harrows, in which the discs are used both for cutting trash and for throwing some of the top soil to the side. Typically, a plurality of disc blades are arranged at a relatively close spacing, and they may be mounted or ganged on a common shaft which extends at an acute angle relative to a line transverse of the direction of travel of the tractor (called the "working angle"). When a gang of disc blades is pulled across a field, complete soil coverage is obtained. That is, all of the soil is tilled, the trash is cut up, mixed with the top soil and some trash is buried. Complete coverage is obtained because the spacing of adjacent discs is typically about forty percent of the diameter of a disc, and the discs are turned slightly to work a path.
In these devices, to reduce the effect of lateral soil displacement due to complete workage, a second line or gang of discs, facing the other direction, may be placed behind a first line.
In one conventional arrangement, each line or gang is formed in a chevron shape. The "V" of the forward line may open toward the front, and the rear line may open toward the rear. This is called a "tandem" arrangement; and both sets of discs are symmetrical about the center line of the system. Another common form of disc harrow, called an "offset" arrangement, has all the discs in the forward gang mounted on a common shaft and facing one lateral direction, and all the discs in the rear gang similarly mounted and facing the other lateral direction. In all such cases, however, the effect is that each disc gang works all of the soil, rather than selected strips, since the primary purpose of the disc is to cut and bury the trash. One disadvantage of a double-working system in addition to the additional horsepower required, is that the rear gang further pulverizes the soil; and this tendency increases with speed. If a farmer then tills the disced land with a chisel plow for deeper working of the soil, the chisel plow also has the effect of digging up the buried trash, and bringing the trash back to the surface.
There is also a plow which uses larger blades (commonly 24-26 inches in diameter) with only one line or gang. The blades are spaced at a distance of about 40% of the diameter of the blades, as with disc gangs. This type of device is referred to as a "one way" tiller because adjacent strips of soil must be worked in the same direction (like a moldboard plow) since the soil is displayed laterally. Because one-ways are used for tillage, with a working angle of about 45.degree., there is a substantial lateral draft when they are used, making them difficult to adjust, particularly in varying soil conditions.
All of the systems mentioned above which employ discs for tillage, as mentioned, normally suggest a lateral spacing of the discs (i.e., the distance between corresponding points on adjacent blades taken along the axis of rotation) which is about 40 percent of the diameter of the blade, although it may range from 30 percent up to 50 percent in an unusual case. With this spacing, when the discs are set at a normal working angle and depth, all of the soil is worked by each set of blades, as mentioned. This spacing has the effect that under conditions of heavy trash or muck or both, the space between blades will become clogged with trash which will accumulate and eventually be left in a large clump. Most such systems are equipped with scraper blades for the discs because the soil and trash became wedged between adjacent blades due to the close spacing.
The large number and closeness of discs in these systems also reduces the weight per disc for a given machine weight, and, therefore, limits penetration of the discs.
Other agricultural implements use disc blades, such as listers and bedders, but the function of the disc blades in these implements is to create raised beds for seeds, with lateral troughs on the top of the soil for wate collection or irrigation.
The present invention is directed to apparatus for primary tillage. That is, it turns up at least some soil at a depth below 3-4 inches (up to about 15 inches), buries a certain amount of trash, and breaks the soil to a depth in the range of 7-15 inches.
A plurality of discs are mounted in a forward set at widely spaced intervals so as to leave alternate strips of worked and unworked soil. By "widely spaced" it is meant that the spacing of the discs along their axis of rotation is greater than 70 percent (about 80 percent in a preferred embodiment) of the diameter of the disc. Preferably, larger discs are used because the apparatus is intended for primary tillage. That is, discs having a diameter in the range of 24-36 inches are preferred. By widely spacing the discs, and arranging the working angle of the discs to be in the range of 25.degree.-30.degree., and preferably about 27.degree., the width of the strips of soil left untilled by the first plurality of discs is substantially equal to the width of the tilled strips.
A second plurality of discs forms a rear set behind the forward set. Each disc of the second set is mounted in a strip of soil left untilled by the first set to complete the working of the top soil in a single pass without re-working any substantial amount of the soil already worked.
A plow tip or point is located immediately behind each of the discs of the second set to break soil at a deeper depth than the associated disc. The plow points may be conventional chisel points or they may be provided with laterally extending wings if it is desired to bring up more deep soil. The discs may be set, for example, to work at a depth of 4-5 inches); and the points may be set to work at a 12 inch depth.
When operating at high speed in the range of 41/2 to 8 mph, each disc of the forward set dips top soil and trash, and throws it laterally. Most of the material is thrown into the furrow formed by the next forward discs, thereby filling that furrow. A dirt shield is located adjacent the leading disc to windrow the soil displaced by it on the adjacent strip of unworked soil. Thus, between adjacent strips of ground worked by the discs of the first set, there are strips of unworked soil. Some soil and trash will accumulate on these previously unworked strips, due to the tilling action of the forward set of discs.
Each disc of the rear set similarly digs top soil and trash, and throws it laterally. But each of the rear discs is immediately followed by a plow point which digs up some soil from a depth deeper than the working depth of the discs. This soil is fractured and contains larger clumps of more compacted soil. The adjacent trailing disc of the rear set then throws the mixed soil and trash which it tills into the furrow formed by the next leading disc/point pair of the rear set to cover the larger clods and tufts left by the point. Thus, the present system leaves a substantially furrowless surface. The windrows formed by the leading discs of the first set (if the first gang is arranged in a chevron form), are gathered by raker blades to cover the furrow formed by the trailing disc/point pairs of the rear set. The raker blades are mounted for independent adjustment both in height and working angle relative to the tilling discs.
In the illustrated embodiment, the plow points are mounted to a main frame which is vertically adjusted by a hydraulic ram. The working depth of the discs is independently adjustable relative to the working depth of the plow points because they ae mounted to subframes which are connected to the main frame by means of an adjusting mechanism.
The adjusting mechanism for changing the depth of the discs relative to the plow points is hydraulic and permits them to be adjusted "on the go" so that the farmer may accommodate the apparatus to varying soil conditions without stopping or even slowing his forward progress.
Because the plow points work beneath furrows formed by the second set of discs, they are able to fracture and break the subsoil into large masses without pulverizing it. This permits water to enter these large cracks and fissures and to continue to work the soil with the freezes and thaws of winter. In the spring, the soil will be soft and mellow because of this, and ready for seed bed preparation with little further working.
Further, the points bring up at least some deep soil, to reduce the problem of herbicide buildup at the surface. Because of the spacing of the plow points and their narrow lower surface, the possibility that these points will register with the exact position taken during a previous year is very small. Hence, there is no formation of plow sole from year to year.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.